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Transcript
INTRODUCTION TO NIGHT LABORATORY
Introduction
Throughout recorded history, and probably long before, people have watched the sky,
seeking comfort in its apparent permanence, but searching for guidance in its changing
aspects for planting of crops, celebration of holidays, or the collection of taxes. Some of
the patterns are obvious; the passing of day and night and the change of the seasons are
so self-evident that we rarely pause to think how fundamentally they regulate our lives.
Less evident to modern city dwellers are the phases of the moon, the motions of the
planets or the changing aspects of the constellations.
As beautiful as a sunset may be or as awe-inspiring as an eclipse of the Sun is, these
events are no longer mysterious. But think of a farmer of 5000 years ago, who had no
clocks or calendars, but still had to know when to plant or to harvest the crops. In those
times, people realized, far more than they do now, how important the celestial cycles are
to our lives and survival.
Inevitably, the human mind seeks to learn the patterns in nature and then to understand
their meaning. The history of Astronomy is a story of the discovery of the sky, its cycles
and our place in the universe.
A. The Nature of Science
Science (and Astronomy in particular) is not at all a static body of knowledge; it is a
dynamic, changing activity, continuously building on what has gone before. In order to
learn about science therefore, it is not enough simply to attempt to memorize a body of
knowledge --- you must also experience, as much as possible, the doing of science.
A common misconception is that scientists either sit alone and somehow gain inspiration
(the image of Newton under the apple tree comes to mind) or they pour random materials
together hoping to concoct new substances. Neither idea is even close to the truth. New
theoretical ideas are always a synthesis of previous ideas and experiments. Experiments
are always designed to test some specific idea. The results of the experiment may be
unexpected and may give rise to completely new ideas, but the original purpose was the
probing of an existing theory.
The purpose of these exercises is to teach you something of the process of doing science.
All of these exercises have been done before of course, but the actual measurements and
observations will be yours. Presumably most of them will lead to the expected results,
more or less; probably several of them will become hopelessly muddled for one reason or
another. This is exactly what one expects to find from “real” experiments being done
for the first time.
B. Astronomical Observations
Although astronomical observations are similar in many respects to laboratory
experimentation in other sciences, there are some important differences. The major
difference is that an astronomer cannot generally control the course of the experiment or
bring the subject into the lab. It is necessary simply to observe --- we are at the mercy of
the phenomenon we wish to study. We cannot make a comet appear at any time but
instead we must wait for one to appear. Nor can we bring a piece of a star into the lab for
chemical analysis, but we must look at it from afar. These obvious, but fundamental,
facts affect the style of observational astronomy as compared to, say, experimental
physics or chemistry. Nevertheless, the basic goals are the same --- to learn about the
nature of the universe in which we live.
Those of us who are professional astronomers enjoy going out at night to study the
universe. Nevertheless, it can be difficult work; especially on a cold winter night the
night seems to last forever. Adding to the discomfort is the frustration of dealing with the
weather; it may take many nights before the weather cooperates. The weather can be
particularly frustrating to beginning students, who typically will have only a few chances
to make their observations. Diligence is the key to success. If there is a good night
coming do not put off your observing --- you may not get another chance.
Another difficulty that you will notice immediately is that the city lights overwhelm the
faint stars; in our modern world, few people can see the stars in their full glory. Because
of the brightness of the night sky, you will not be able to pick out the constellations as
well as people used to do, and even with a telescope, faint nebulae and galaxies will be
something of a disappointment. Astronomers in fact talk about “light pollution” and
build observatories on distant mountaintops, far from the city.
C. Practical Considerations
Since the whole point of these exercises is to give you a feeling of what it means to do
science, your success will depend to a large extent on active and regular participation. A
careful and complete job in taking notes of what you have done will be a major help in
ensuring a good grade for the course. Keeping good records is also an essential aspect of
doing any scientific work. Remember also that many observations can only be made
once, and you may not always realize what is useful until later, so you must record
everything that may possibly be relevant and useful. Most of the time, the data pages at
the end of this lab book will guide you as to what sorts of information you should
include, but you should not hesitate to make note of anything else that seems relevant.
Because astronomical observations are affected so strongly by the conditions of the sky,
you should always record the weather conditions before doing anything else. All factors
that appear to be relevant should be recorded, including any changes that may occur
during your observations. At the very least, the following information should be
included:
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•
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the date
starting time
ending time
wind
temperature
sky conditions (clear, cloudy, hazy, etc.)
the moon (phase and location, if visible)
additional comments
Whenever you come to the observatory or lab sections you should bring the following:
1. Your lab book;
2. Two pens.
For the night labs you should also bring:
3. A small flashlight;
4. Your star atlas or night sky guide or star wheel;
5. WARM CLOTHING ON COOL AND WINTER EVENINGS.
One cannot stress this last item too much. On a winter night, an observatory can seem
like the coldest place on earth. Several layers of clothing and WARM BOOTS are
essential.
D. Lab Reports
The data you will gather for these exercises will be entered onto your data pages,
(notebook paper is fine). In general, you must have each data page initialed by one of the
instructors. In preparing your report for any labs, keep in mind the following goal: If you
read the report in six months, it should be possible to reconstruct what was actually done
and what the principal conclusions are.